The relationship for hydro dynamic parameters (flow regime, flow velocity, depth and friction factor) as a function of flow discharge and slope gradient was simulated by means of flume experiments. The results demonstrate that when flow depth is less than 0.316 cm, the flow is transitional flow. The flow change to turbulent when flow depth is large than 0.316cm. The flow velocity and depth are mainly controlled by flow discharge, simple linear function can be used for mean velocity and flow depth predicting. Slope gradient has no significant impact on both flow velocity and depth and has influence on friction factor at low flow discharge. However, as discharge increasing, the friction factor will be controlled by discharge again. All these results reveal that there is larger difference exiting in hydrodynamic properties between overland flow and open channel flow, and should be full considered in water erosion mechanism analyzing and model building.